Jeremy Corbyn has poured cold water over calls for Labour to back a second referendum on the UK's membership of the EU - saying it is "an option for the future" but "not an option for today".
The Labour leader also revealed that if there was another referendum he did not know how he would vote.
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Mr Corbyn, in an interview with Sky News' Sophy Ridge On Sunday programme, also told how his party "couldn't stop" Brexit because of the parliamentary arithmetic.
He said: "We couldn't stop it because we don't have the votes in Parliament to do so.
"There was a referendum in 2016, a majority voted to leave the EU, there are many reasons why people voted. I don't think you call a referendum and then say you don't like the result and go away from it, you've got to understand why people voted and negotiate the best deal you can," he added.
Asked about calls for a second referendum Mr Corbyn said: "It's an option for the future but it's not an option for today, if there was a referendum tomorrow what's it going to be on, what's the question going to be?"
Mr Corbyn, on which way he would vote in such a referendum, said: "I don't know how I am going to vote, what the options would be at that time."
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The Labour leader also trashed Theresa May's Brexit deal, telling Sky News that it was a "one-way agreement" in which the EU "calls all the shots".
He said: "We'll vote against this deal because it doesn't meet our tests. We don't believe it serves the interest of this country, therefore the Government have to go back to the EU and renegotiate rapidly.
"There's 500 pages in this document much of which is quite vague, where's the guarantee on environmental protections, where's the guarantee on consumer protections, where's the guarantee on workers' rights?"
Mr Corbyn said Labour would focus on negotiating a permanent customs arrangement with the EU, as if this was not agreed the UK would "lose on jobs, lose on investment and we lose on future economic development".
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Shadow attorney general Shami Chakrabarti, appearing on BBC One's Andrew Marr Show, later said that Mrs May's Brexit deal was "the worst kind of bureaucratic fudge that doesn't deliver for anyone".
Baroness Chakrabarti said the deal had been "designed to look as if it can please everybody and it can't" and if it were to be rejected by the Commons Mrs May "ought to go to the country" with it.